Printed Stretch Sensor

ABSTRACT

Disclosed is a patterned article comprising: (1) a deformable nonconductive substrate; (2) an imagewise pattern thereon of a conductive stretchable ink; and (3) an external circuit connecting the imagewise pattern, the external circuit being capable of measuring the electrical resistance across regions of the deformable nonconductive substrate and determining the degree of deformation thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

Reference is made to Copending application Ser. No. 13/182,579, filedJul. 14, 2011, entitled “Stretchable Ink Composition,” with the namedinventors Yiliang Wu, Qi Zhang, Ke Zhou, Yu Qi, and Nan-Xing Hu, thedisclosure of which is totally incorporated herein by reference.

BACKGROUND

Disclosed herein is a printed stretch sensor that can be prepared byprinting methods such as ink jet printing.

Stretch sensors typically come in a one-dimensional form (onlystretching across a single axis). By weaving or knitting stretch sensorsinto a fabric, multiple degrees of freedom can be achieved.Stretch-sensitive material can also be glued onto an elastic surface,but these techniques are labor-intensive and result in limited range ofmotion. By creating printed stretch sensors on an elastic surface, onecan achieve high range of motion, and manufacture is as simple asprinting a material onto a surface.

Conductive elastomers are used in applications requiring deformabilityand electrical conductivity, such as for gaskets used in EMI-shielding.One notable feature of conductive elastomers is that they changeconductivity as they are stretched. By measuring the electricalresistance through such a material, one can calculate the degree ofstretch.

Conductive stretchable inks are known, as disclosed in, for example,“Inkjet-Printed Stretchable Silver Electrode on Wave StructuredElastomeric Substrate,” Seungjun Chung, Jaemyon Lee, Hyunsoo Song,Sangwoo Kim, Jaewook Jeong, and Yongtaek Hong, Applied Physics Letters,98, 153110 (2011) and Copending application Ser. No. 13/182,579, filedJul. 14, 2011, entitled “Stretchable Ink Composition,” with the namedinventors Yiliang Wu, Qi Zhang, Ke Zhou, Yu Qi, and Nan-Xing Hu, thedisclosures of each of which are totally incorporated herein byreference.

Much of the work related to conductive elastomers has attempted toovercome the challenge of conductivity loss during deformation. Incontrast, the articles disclosed herein take advantage of this property.

Accordingly, while known articles and compositions are suitable fortheir intended purposes, a stretch sensor which stretches in twodimension (i.e., along two axes) that can be prepared by printing aconductive ink in an imagewise pattern onto a deformable nonconductivesubstrate in such a way that both materials can stretch and return backto their original shape is desirable.

SUMMARY

Disclosed herein is a patterned article comprising: (1) a deformablenonconductive substrate; (2) an imagewise pattern thereon of aconductive stretchable ink; and (3) an external circuit connecting theimagewise pattern, said external circuit being capable of measuring theelectrical resistance across regions of the deformable nonconductivesubstrate and determining the degree of deformation thereof. Alsodisclosed herein is a patterned article comprising: (1) a deformablenonconductive substrate having a resistivity of at least about 1.8×10⁵Ωm and an elasticity in the direction of elongation of at least about0.0008 MPa; (2) an imagewise pattern thereon of a conductive stretchableink having a conductivity of from about 0.01 μS to about 100 MS andcomprising a fluoroelastomer; and (3) an external circuit connecting theimagewise pattern, said external circuit being capable of measuring theelectrical resistance across regions of the deformable nonconductivesubstrate and determining the degree of deformation thereof. Furtherdisclosed herein is a process which comprises: (a) applying to adeformable nonconductive substrate in an imagewise pattern a conductivestretchable ink; (b) connecting the imagewise pattern with an externalcircuit; and (c) measuring the electrical resistance across regions ofthe deformable nonconductive substrate and determining the degree ofdeformation thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate a first embodiment of the articles andapparatus disclosed herein.

FIGS. 2A and 2B, 3, 4, and 5A, 5B, and 5C illustrate a second embodimentof the articles and apparatus disclosed herein wherein apressure-sensitive touch sensor is demonstrated.

FIGS. 6 and 7A and 7B illustrate a third embodiment of the articles andapparatus disclosed herein wherein a pressure-sensitive weighing deviceis demonstrated.

DETAILED DESCRIPTION

The articles and apparatus disclosed herein comprise conductive inksprinted onto nonconductive deformable substrates. By “nonconductive” ismeant herein a substrate having a resistivity of in one embodiment atleast about 1.8×10⁵ Ωm, in another embodiment at least about 100 MΩm(100 megaΩm; 1×10⁶ Ωm), in yet another embodiment at least about 1 GΩm(1 gigaΩm; 1×10⁹ Ωm), and in still another embodiment at least about 100GΩm, with no upper limit on resistivity, although the value can beoutside of these ranges.

The substrate is deformable. By “deformable” is meant herein a substratehaving high elasticity in the direction of deformation, in oneembodiment at least about 0.0008 MPa (megaPascals), in anotherembodiment at least about 0.0009 MPa, in yet another embodiment at leastabout 0.001 PMa, in still another embodiment at least about 0.008 MPa,in yet another embodiment at least about 0.009 MPa, and in still anotherembodiment at least about 0.01 MPa, and in one embodiment no more thanabout 0.1 MPa, in another embodiment no more than about 0.09 MPa, in yetanother embodiment no more than about 0.08 MPa, and in still anotherembodiment no more than about 0.01 MPa, although the value can beoutside of these ranges.

Examples of suitable substrates include (but are not limited to) rubber,such as natural polyisoprene, polybutadiene rubber, chloroprene rubber,neoprene rubber, butyl rubber (copolymer of isobutylene and isoprene),styrene-butadiene rubber, silicon rubber, nitrile rubber (which is acopolymer of butadiene and acrylonitrile), ethylene propylene rubber,ethylene propylene diene rubber, epichlorohydrin rubber, polyacrylicrubber, ethylene-vinyl acetate, polyether block amides, polysulfiderubber, chlorosulfonated polyethylene as HYPALON, or the like. In aspecific embodiment, the inks disclosed herein can be printed on asilicon rubber, polyacrylic rubber, butyl rubber, or neoprene rubbersubstrate and the imaged substrate can be stretched in one axialdirection (i.e., along the x-axis, as opposed to both the x-axis and they-axis) to in one embodiment at least 110%, in another embodiment atleast 150%, and in yet another embodiment at least 200%, of the lengthof its original dimension in one embodiment at least about 50 times, inanother embodiment at least about 100 times, and in yet anotherembodiment at least about 500 times, without exhibiting cracks ordelamination.

An imagewise pattern is printed onto the deformable substrate with aconductive stretchable ink. By “conductive is meant herein aconductivity of in one embodiment at least about 0.01 μS (microSiemen),and in another embodiment at least about 0.05 S (Siemen), and in oneembodiment no more than about 100 MS (megaSiemens), although the valuecan be outside of these ranges.

The ink is one suitable for ink jet printing onto the substrate. In oneembodiment, the ink composition is a low-viscosity composition. The term“low-viscosity” is used in contrast to conventional high-viscosity inkssuch as screen printing inks, which tend to have a viscosity of at least1,000 centipoise (cps). In specific embodiments, the ink disclosedherein has a viscosity of in one embodiment no more than about 100 cps,in another embodiment no more than about 50 cps, and in yet anotherembodiment no more than about 20 cps, although the viscosity can beoutside of these ranges. When used in ink jet printing applications, theink compositions are generally of a viscosity suitable for use in saidink jet printing processes. For example, for thermal ink jet printingapplications, at room temperature (i.e., about 25° C.), the inkviscosity is in one embodiment at least about lcps and in one embodimentis no more than about 10 cps, in another embodiment no more than about 7cps, and in yet another embodiment no more than about 5 cps, althoughthe viscosity can be outside of these ranges. For example, forpiezoelectric ink jet printing, at the jetting temperature, the inkviscosity is in one embodiment at least about 2 cps, and in anotherembodiment at least about 3 cps, and in one embodiment is no more thanabout 20 cps, in another embodiment no more than about 15 cps, and inyet another embodiment no more than about 10 cps, although the viscositycan be outside of these ranges. The jetting temperature can be as low asabout 20 to 25° C., and can be in one embodiment as high as about 90°C., in another embodiment as high as about 60° C., and in yet anotherembodiment as high as about 40° C., although the jetting temperature canbe outside of these ranges.

In one specific embodiment, the ink contains a fluoroelastomer asdisclosed in Copending application Ser. No. 13/182,579, the disclosureof which is totally incorporated herein by reference. An elastomer isdefined by the Collins English Dictionary as any material, such asnatural or synthetic rubber, that is able to resume its original shapewhen a deforming force is removed. A fluoroelastomer, for the purposesof the present disclosure, is a fluoropolymer that behaves according tothis definition of an elastomer.

The elastomeric fluoropolymer can be a perfluoropolymer or it cancontain atoms other than carbon and fluorine, such as hydrogen, chlorineand other halogens, oxygen, nitrogen, sulfur, silicon, and the like, aswell as mixtures thereof. The term “fluoropolymer” is intended to denoteany polymer comprising more than 25 percent by weight of recurringmonomer units derived from at least one ethylenically unsaturatedmonomer comprising at least one fluorine atom (hereinafter, fluorinatedmonomer). When the fluorinated monomer is free of hydrogen atoms andcontains other halogen atoms, it is referred to as aper(halo)fluoromonomer. When the fluorinated monomer contains hydrogenatoms, it is referred to as a hydrogen-containing fluorinated monomer.Examples of common fluorinated monomers include, but are not limited to,tetrafluoroethylene (TFE); C₃-C₈ perfluoroolefins, such ashexafluoropropene (HFP); C₂-C₈ hydrogenated monofluoroolefins, such asvinyl fluoride; vinylidene fluoride (VdF); 1,2-difluoroethylene andtrifluoroethylene; perfluoroalkylethylenes complying with formulaCH₂═CH—R_(f0), in which R_(f0) is a C₁-C₆ perfluoroalkyl, chloro- and/orbromo- and/or iodo-C₂-C₆ fluoroolefins, like chlorotrifluoroethylene(CTFE); (per)fluoroalkylvinylethers (PAVE) complying with formulaCF₂═CFOR_(f1) in which R_(f1) is a C₁-C₆ fluoro- or perfluoroalkyl, e.g.CF₃, C₂F₅, C₃F₇; CF₂═CFOX₀ (per)fluoro-oxyalkylvinylethers, in which X₀is a C₁-C₁₂ alkyl, or a C₁-C₁₂ oxyalkyl, or a C₁-C₁₂ (per)fluorooxyalkylhaving one or more ether groups, like perfluoro-2-propoxy-propyl;(per)fluoromethoxyalkylvinylethers complying with formulaCF₂═CFOCF₂OR_(f2) in which R_(f2) is a C₁-C₆ fluoro- or perfluoroalkyl,e.g. CF₃, C₂F₅, C₃F₇ or a C₁-C₆ (per)fluorooxyalkyl having one or moreether groups, like —C₂F₅—O—CF₃; functional (per)fluoroalkylvinyletherscomplying with formula CF₂═CFOY₀, in which Y₀ is a C₁-C₁₂ alkyl or(per)fluoroalkyl, or a C₁-C₁₂ oxyalkyl, or a C₁-C₁₂ (per)fluorooxyalkylhaving one or more ether groups and Y₀ comprising a carboxylic orsulfonic acid group, in its acid, acid halide or salt form;fluorodioxoles, especially perfluorodioxoles; and the like. Copolymersof two or more fluorinated monomers are also possible.

The fluoropolymer can be a copolymer containing fluorinated monomers aswell as hydrogenated monomers (a term referring to monomers free offluorine atoms for the purposes of the present disclosure). Examples ofsuitable hydrogenated monomers include, but are not limited to,ethylene, propylene, vinyl monomers such as vinyl acetate, acrylicmonomers, such as methyl methacrylate, acrylic acid, methacrylic acid,ethylacrylate, n-butylacrylate, hydroxypropylacrylate,(hydroxy)ethylhexylacrylate, and hydroxyethyl acrylate, and the like,styrene monomers, like styrene and p-methylstyrene, vinyl ethers, suchas propylvinylether, cyclohexylvinylether, vinyl-4-hydroxybutylether,unsaturated carboxylic acids, such as vinylacetic acid, and the like, aswell as mixtures thereof.

Some specific examples of suitable fluoroelastomers include (but are notlimited to) fluoro rubbers of the polymethylene type that use vinylidenefluoride as a comonomer and have substituent fluoro, alkyl,perfluoroalkyl, or perfluoroalkyoxy groups in the polymer chain, with orwithout a curesite monomer, such as copolymers of vinylidene fluorideand hexafluoropropylene; terpolymers of vinylidene fluoride,hexafluoropropylene, and tetrafluoroethylene; copolymers of vinylidenefluoride and (per)fluoromethoxyalkylvinylethers; terpolymers ofvinylidene fluoride, hexafluoropropylene, andpolyperfluoromethylvinylether; terpolymers of vinylidene fluoride,tetrafluoroethylene, and a fluorinated vinyl ether; terpolymer ofvinylidene fluoride, tetrafluoroethylene, and propylene; tetrapolymersof vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, andpolyperfluoromethylvinylether; terpolymers of tetrafluoroethylene,propylene, and vinylidene fluoride; pentapolymers oftetrafluoroethylene, hexafluoroethylene, vinylidene fluoride, ethylene,and polyperfluoromethylvinylether; perfluoro rubbers of thepolymethylene type having all substituent groups on the polymer chaineither fluoro, perfluoroalkyl, or perfluoroalkyoxyl groups; fluororubbers of the polymethylene type containing one or more of themonomeric alkyl, perfluoroalkyl, and/or perfluoroalkoxy groups with orwithout a curesite monomer; and the like, as well as mixtures thereof.One specific example of a suitable fluoroelastomer is commerciallyavailable as TECNOFLON® TN latex from Solvay Solexis. Other commerciallyavailable fluoroelastomers such as VITON® from DuPont, DYNEON™ from 3 M,AFLAS®, DAI-EL™ from Daikin, and the like can be used as well.

In one embodiment, the fluoroelastomer has a fluorine content of atleast about 5 weight %, in another embodiment at least about 10 weight%, and in yet another embodiment at least about 30 weight %, and in oneembodiment no more than about 76 weight % (perfluoroelastomer), inanother embodiment no more than about 70 weight %, and in yet anotherembodiment no more than about 68 weight %, although the fluorine contentcan be outside of these ranges.

In one embodiment, the fluoroelastomer has a tensile strength of atleast about 3 MPa, in another embodiment at least about 4 MPa, and inyet another embodiment at least about 7 MPa, and in one embodiment nomore than about 25 MPa, in another embodiment no more than about 20 MPa,and in yet another embodiment no more than about 18 MPa, as measured byASTM D412C, although the tensile strength can be outside of theseranges.

In one embodiment, the fluoroelastomer has an elongation at break of atleast about 150%, in another embodiment at least about 200%, and in yetanother embodiment at least about 400%, and in one embodiment no morethan about 1100%, in another embodiment no more than about 1000%, and inyet another embodiment no more than about 800%, as measured by ASTMD412C, although the elongation at break can be outside of these ranges.

In one embodiment, the fluoroelastomer has a hardness (Shore A) value ofat least about 20, in another embodiment at least about 30, and in yetanother embodiment at least about 40, and in one embodiment no more thanabout 90, in another embodiment no more than about 85, and in yetanother embodiment no more than about 80, as measured by ASTM 2240,although the hardness can be outside of these ranges.

In one embodiment, the fluoroelastomer has a glass transitiontemperature of at least about −70° C., in another embodiment at leastabout −50° C., and in yet another embodiment at least about −40° C., andin one embodiment no more than about 25° C., in another embodiment nomore than about 0° C., and in yet another embodiment no more than about−10° C., although the Tg can be outside of these ranges.

The fluoroelastomer is present in the ink in any desired or effectiveamount, in one embodiment at least about 0.1 percent by weight of theink, in another embodiment at least about 1 percent by weight of theink, and in yet another embodiment at least about 2 percent by weight ofthe ink, and in one embodiment no more than about 25 percent by weightof the ink, in another embodiment no more than about 20 percent byweight of the ink, and in yet another embodiment no more than about 15percent by weight of the ink, although the amount can be outside ofthese ranges.

When the inks contain a fluoroelastomer, the inks disclosed herein alsocontain a surfactant. Any surfactant that forms an emulsion of thefluoroelastomer in the ink can be employed. Examples of suitablesurfactants include anionic surfactants, cationic surfactants, nonionicsurfactants, zwitterionic surfactants, and the like, as well as mixturesthereof. Examples of suitable surfactants include alkyl polyethyleneoxides, alkyl phenyl polyethylene oxides, polyethylene oxide blockcopolymers, acetylenic polyethylene oxides, polyethylene oxide(di)esters, polyethylene oxide amines, protonated polyethylene oxideamines, protonated polyethylene oxide amides, dimethicone copolyols,substituted amine oxides, and the like, with specific examples includingprimary, secondary, and tertiary amine salt compounds such ashydrochloric acid salts, acetic acid salts of laurylamine, coconutamine, stearylamine, rosin amine; quaternary ammonium salt typecompounds such as lauryltrimethylammonium chloride,cetyltrimethylammonium chloride, benzyltributylammonium chloride,benzalkonium chloride, etc.; pyridinium salty type compounds such ascetylpyridinium chloride, cetylpyridinium bromide, etc.; nonionicsurfactant such as polyoxyethylene alkyl ethers, polyoxyethylene alkylesters, acetylene alcohols, acetylene glycols; and other surfactantssuch as 2-heptadecenyl-hydroxyethylimidazoline,dihydroxyethylstearylamine, stearyldimethylbetaine, andlauryldihydroxyethylbetaine; fluorosurfactants; and the like, as well asmixtures thereof. Additional examples of nonionic surfactants includepolyacrylic acid, methalose, methyl cellulose, ethyl cellulose, propylcellulose, hydroxy ethyl cellulose, carboxy methyl cellulose,polyoxyethylene cetyl ether, polyoxyethylene lauryl ether,polyoxyethylene octyl ether, polyoxyethylene octylphenyl ether,polyoxyethylene oleyl ether, polyoxyethylene sorbitan monolaurate,polyoxyethylene stearyl ether, polyoxyethylene nonylphenyl ether,dialkylphenoxy poly(ethyleneoxy)ethanol, available from Rhone-Poulenc asIGEPAL CA-210™ IGEPAL CA-520™, IGEPAL CA-720™, IGEPAL CO-890™, IGEPALCO-720™, IGEPAL CO-290™, IGEPAL CA-210™, ANTAROX 890™, and ANTAROX 897™.Other examples of suitable nonionic surfactants include a blockcopolymer of polyethylene oxide and polypropylene oxide, including thosecommercially available as SYNPERONIC PE/F, such as SYNPERONIC PE/F 108.Other examples of suitable anionic surfactants include sulfates andsulfonates, sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate, sodium dodecylnaphthalene sulfate, dialkyl benzenealkylsulfates and sulfonates, acids such as abitic acid available fromAldrich, NEOGEN R™, NEOGEN SC™ available from Daiichi Kogyo Seiyaku,combinations thereof, and the like. Other examples of suitable anionicsurfactants include DOWFAX™ 2A1, an alkyldiphenyloxide disulfonate fromDow Chemical Company, and/or TAYCA POWER BN2060 from Tayca Corporation(Japan), which are branched sodium dodecyl benzene sulfonates. Otherexamples of suitable cationic surfactants, which are usually positivelycharged, include alkylbenzyl dimethyl ammonium chloride, dialkylbenzenealkyl ammonium chloride, lauryl trimethyl ammonium chloride,alkylbenzyl methyl ammonium chloride, alkyl benzyl dimethyl ammoniumbromide, benzalkonium chloride, cetyl pyridinium bromide, C₁₂, C₁₅, C₁₇trimethyl ammonium bromides, halide salts of quaternizedpolyoxyethylalkylamines, dodecylbenzyl triethyl ammonium chloride,MIRAPOL™ and ALKAQUAT™, available from Alkaril Chemical Company,SANIZOL™ (benzalkonium chloride), available from Kao Chemicals, and thelike, as well as mixtures thereof. Mixtures of any two or moresurfactants can be used. The surfactant is present in any desired oreffective amount, in one embodiment at least about 0.01 percent byweight of the ink, and in one embodiment no more than about 5 percent byweight of the ink, although the amount can be outside of these ranges.

The ink further contains a conductive component. Any desired oreffective conductive component can be employed. Examples include (butare not limited to) carbon black, polypyrrole, polyacetylene,polyaniline, polyphenylene vinylene, polythiophene, polyphenylenesulfide, graphene, silver nanoparticles, copper nanoparticles, or thelike, as well as mixtures thereof.

In one specific embodiment, the ink is of a material that containssubstantially no silver nanoparticles. In another specific embodiment,the ink is of a material that contains substantially no coppernanoparticles. By “nanoparticles” is meant particles having an averageparticle diameter of no more than about 100 nm.

The conductive component is present in the ink in any desired oreffective amount, in one embodiment at least about 52 percent by volumeof the dried or cured ink, in another embodiment at least about 56percent by volume of the dried or cured ink, and in yet anotherembodiment at least about 61 percent by volume of the dried or curedink, and in one embodiment no more than about 74 percent by volume ofthe dried or cured ink, in another embodiment no more than about 70percent by volume of the dried or cured ink, and in yet anotherembodiment no more than about 65 percent by volume of the dried or curedink, although the amount can be outside of these ranges.

The ink composition can further comprise crosslinkers. In embodiments,the crosslinker is an organoamine, a dihydroxy aromatic compound, aperoxide, a metal oxide, or the like, as well as mixtures thereof.Crosslinking can further enhance the physical properties of the imagesgenerated from the ink composition. The crosslinker can be present inany desired or effective amount, in one embodiment at least about 0.1percent by weight of the ink, in another embodiment at least about 1percent by weight of the ink, and in yet another embodiment at leastabout 5 percent by weight of the ink, and in one embodiment no more thanabout 20 percent by weight of the ink, in another embodiment no morethan about 15 percent by weight of the ink, and in yet anotherembodiment no more than about 10 percent by weight of the ink, althoughthe amount can be outside of these ranges.

The conductive ink is printed onto the deformable substrate in an imagepattern. The ink compositions can be used in a process which entailsincorporating the ink composition into an ink jet printing apparatus andcausing droplets of the ink to be ejected in an imagewise pattern onto asubstrate. In a specific embodiment, the printing apparatus employs athermal ink jet process wherein the ink in the nozzles is selectivelyheated in an imagewise pattern, thereby causing droplets of the ink tobe ejected in imagewise pattern. In another embodiment, the printingapparatus employs an acoustic ink jet process wherein droplets of theink are caused to be ejected in imagewise pattern by acoustic beams. Inyet another embodiment, the printing apparatus employs a piezoelectricink jet process, wherein droplets of the ink are caused to be ejected inimagewise pattern by oscillations of piezoelectric vibrating elements.

In one embodiment, the inks disclosed herein can be printed on a rubbersubstrate, such as natural polyisoprene, polybutadiene rubber,chloroprene rubber, neoprene rubber, butyl rubber (copolymer ofisobutylene and isoprene), styrene-butadiene rubber, silicon rubber,nitrile rubber (which is a copolymer of butadiene and acrylonitrile),ethylene propylene rubber, ethylene propylene diene rubber,epichlorohydrin rubber, polyacrylic rubber, ethylene-vinyl acetate,polyether block amides, polysulfide rubber, chlorosulfonatedpolyethylene as HYPALON, or the like. In a specific embodiment, the inksdisclosed herein can be printed on a silicon rubber, polyacrylic rubber,butyl rubber, or neoprene rubber substrate and the imaged substrate canbe stretched in one axial direction (i.e., along the x-axis, as opposedto both the x-axis and the y-axis) to in one embodiment at least 110%,in another embodiment at least 150%, and in yet another embodiment atleast 200%, of the length of its original dimension in one embodiment atleast about 50 times, in another embodiment at least about 100 times,and in yet another embodiment at least about 500 times, withoutexhibiting cracks or delamination.

In one embodiment, the inks disclosed herein can be printed on a siliconrubber, polyacrylic rubber, butyl rubber, or neoprene rubber substrateand the imaged substrate can be submerged in water for in one embodimentat least about 1 day, in another embodiment for at least about 1 week,and in yet another embodiment for at least about 1 month, withoutexhibiting damage to the imagewise pattern.

In a specific embodiment, the images generated with the inks disclosedherein are highly water-resistant. In one embodiment, images generatedwith the inks exhibit a water droplet contact angle of at least about80°, in another embodiment at least about 90°, and in yet anotherembodiment at least about 95°, although the contact angle can be outsideof these ranges. The water-resistant characteristic renders the inkdisclosed herein suitable for outdoor applications or printing onwater-related products such vehicle wrap, swimming suits, and the like.

In a specific embodiment, the images generated with the inks disclosedherein have a good chemical resistance. For example, they can exhibitgood to excellent resistance toward alcohols, acetic acid, acetamide,allyl bromide, allyl chloride, benzoyl chloride, ethers, esters,hydrocarbons, blood, salt solutions, and the like.

In one embodiment, the images generated with the inks disclosed hereinhave a tensile strength of at least about 3 MPa, in another embodimentat least about 4 MPa, and in yet another embodiment at least about 8MPa, and in one embodiment no more than about 25 MPa, in anotherembodiment no more than about 20 MPa, and in yet another embodiment nomore than about 18 MPa, as measured by ASTM D412C, although the tensilestrength can be outside of these ranges.

In one embodiment, the images generated with the inks disclosed hereinhave an elongation at break of at least about 150%, in anotherembodiment at least about 200%, and in yet another embodiment at leastabout 400%, and in one embodiment no more than about 1000%, in anotherembodiment no more than about 800%, and in yet another embodiment nomore than about 700%, as measured by ASTM D412C, although the elongationat break can be outside of these ranges. Generally, the images have alarger elongation at break than that of the deformable substrate.

In one embodiment, the images generated with the inks disclosed hereinhave a hardness (Shore A) value of at least about 20, in anotherembodiment at least about 30, and in yet another embodiment at leastabout 40, and in one embodiment no more than about 100, in anotherembodiment no more than about 90, and in yet another embodiment no morethan about 85, as measured by ASTM 2240, although the hardness can beoutside of these ranges.

An external circuit connects the imagewise pattern. The external circuitis capable of measuring the electrical resistance across regions of thedeformable nonconductive substrate and determining the degree ofdeformation thereof. In its simplest embodiment, illustrated in FIGS. 1Aand 1B, a single line 1 of the conductive stretchable ink is printedonto the deformable nonconductive substrate 3 and the distal ends 5 and7 of line 1 are connected with an external circuit 9 and ohmmeter 11 tomeasure the resistivity across line 1. As shown on the “relaxed” imageand substrate in FIG. 1A, the resistivity of line 1 is lower than it ison the “stretched” image and substrate in FIG. 1B. The degree ofresistivity for the specific ink material can be correlated to thedegree of stretch. The correlation between degree of stretch andresistivity will vary depending on the selected materials andformulation, and can be determined experimentally for the selectedarticle.

In another embodiment, as illustrated in FIGS. 2A and 2B, 3, 4, and 5A,5B, and 5C, a touch sensitive array 100 is provided that can pinpointthe precise location of a touch on a surface. On opposite sides A and Bof a deformable nonconductive substrate 103 are printed lines 101 (shownas 101 a on surface A and 101 b on surface B) of a conductivestretchable ink in alternating orientations so that the resultingconfiguration forms a grid. Lines 101 a do not cross each other. Lines101 b do not cross each other. At least some of lines 101 a cross atleast some of lines 101 b. In one specific embodiment, the grid lines101 a are substantially perpendicular to lines 101 b. Opposite sides areused so that the electrically conductive traces do not cross one anotherand form a short. At each end of the conductive lines 101 are enlargedpads 105 and 107 (shown as 105 a on surface A and 105 b on surface B,and 107 a on surface A and 107 b on surface B) to facilitate electricalconnections. As shown in FIG. 4, permanent connections can be made bysecurely gluing on flexible ribbon cables 109 with conductive adhesive110.

Each line of printed conductive stretchable ink 101 is configured as aloop in a resistance measuring circuit. As shown in FIG. 5A, a touch istaking place, depicted by sphere 113 deforming the deformablenonconductive substrate 103. In this state, one can sample theresistance in each loop and determine which loops are experiencing peakresistance. These loops will be the ones intersecting with the touchlocation. Using two sets of loops, one for the X-coordinate and one forthe Y-coordinate, one can pinpoint the exact location of the touch asindicated by the plots shown in FIGS. 5B and 5C. The loops are attachedto an external circuit that measures resistance and processes the datato come up with a derived value such as the mass of an object or a valuethat can be compared with values from adjacent loops to determine thelocality of maximum deformation. Such a material can be stretched acrossa springy foam backing to create a fingertip-like device that willregister touches, when deformed, and then return back to its originalshape and resistance signature, when not. This device can be used, forexample, in industrial robotics applications, where a sensitive touchresponse would allow equipment to operate more effectively. For example,in applications wherein a robot lifts an article, this device can beemployed to detect whether the robot is holding the article securely ornot.

In yet another embodiment, as illustrated in FIGS. 6 and 7A and 7B, aprinted weighing device 200 is provided. On a deformable nonconductivesubstrate 203 is printed one or more lines 201 of a conductivestretchable ink. The term “lines” here includes straight lines as wellas wavy lines, curves, or the like, provided that the printed articleprovides measurable, continuous changes in resistance when deformed. Ateach end of the conductive line or lines 201 are enlarged pads 205 and207 to facilitate electrical connections (not shown). Circuitry can becompleted as shown in FIG. 1. Articles of varying mass 215 a and 215 bare placed on the deformable nonconductive substrate 203 printed with apattern 201 of conductive material, the conductivity of which decreaseswith the degree of stretch, and the conductive material 201 stretches toa different degree with different amounts of mass. Likewise, themeasured resistance through the conductive pattern will increase in arepeatable way relative to the degree of stretch so that a particularmass will correspond to a specific resistance measurement, and one candeduce the mass of an object by measuring the resistance through theconductive printed material. The correlation between degree of stretchand resistivity will vary depending on the selected materials andformulation, and can be determined experimentally for the selectedarticle.

Specific embodiments will now be described in detail. These examples areintended to be illustrative, and the claims are not limited to thematerials, conditions, or process parameters set forth in theseembodiments. All parts and percentages are by weight unless otherwiseindicated.

Example I

A fluoroelastomer emulsion (TECNOFLON® TN latex, Solvay Solexis Inc.,West Deptford, N.J., solids content 64.91 wt %) is mixed with carbonblack (solid contents 19.96%, also containing sodium dodecyl benzenesulfonate surfactant in an amount of 2 wt. %) to form a homogenousdispersion in which the solids content contains 5 wt. % pigment. Themixture is first diluted with distilled water until a suitable viscosity(˜5 cps) is achieved for ink jet printing. Ethylene glycol is then addedinto the diluted mixture at a 1:9 ratio (1 part by weight ethyleneglycol per 9 parts by weight mixture) to prevent the dispersion fromdrying in the nozzle. This jettable ink is printed on a natural latexrubber substrate (latex glove) using a DMP-2800 ink jet printer (FujiFilm Dimatix, Santa Clara, Calif.) equipped with 10 pL cartridges(DMC-11610). After printing, the ink solvents are dried at 60° C. forabout 5 min. It is believed that the images thus generated will be ableto be stretched in both directions up to 500% (which is the limit of thesubstrate), and that after hundreds of stretch-relaxation cycles, theimages will stay firmly on the substrate without any damage such ascracks or de-lamination. It is also believed that the printed images,when tested against water exposure by brushing them under water, willexhibit no visible damage.

Example II

The process of Example I is repeated except that a polydimethylsiloxane(PDMS) silicon rubber substrate is used. The PDMS substrate is made inthe laboratory using Dow Corning SYLGARD 184 kit. It is believed thatsimilar results will be obtained, and that the printed image will beable to be stretched up to 200% (limit of the PDMS substrate) forhundreds of cycles without visible damage.

Example III

The process of Example I is repeated except that anotherfluoroelastomer, DYNEON™ FX 10180 fluoroelastomer (terpolymer latex ofvinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene) isused instead of the TECNOFLON® TN. It is believe that similar resultswill be observed.

Example IV

The process of Example I is repeated except that another conductivepigment, polypyrrole, is used instead of the carbon black. It is believethat similar results will be observed.

Example V

The process of Example I is repeated except that another conductivepigment, polyacetylene, is used instead of the carbon black. It isbelieve that similar results will be observed.

Example VI

The process of Example I is repeated except that another conductivepigment, polyphenylene sulfide, is used instead of the carbon black. Itis believe that similar results will be observed.

Other embodiments and modifications of the present invention may occurto those of ordinary skill in the art subsequent to a review of theinformation presented herein; these embodiments and modifications, aswell as equivalents thereof, are also included within the scope of thisinvention.

The recited order of processing elements or sequences, or the use ofnumbers, letters, or other designations therefor, is not intended tolimit a claimed process to any order except as specified in the claimitself.

What is claimed is:
 1. A patterned article comprising: (1) a deformablenonconductive substrate; (2) an imagewise pattern thereon of aconductive stretchable ink; and (3) an external circuit connecting theimagewise pattern, said external circuit being capable of measuring theelectrical resistance across regions of the deformable nonconductivesubstrate and determining the degree of deformation thereof.
 2. Anarticle according to claim 1 wherein the deformable nonconductivesubstrate has a resistivity of at least about 1.8×10⁵ Ωm.
 3. An articleaccording to claim 1 wherein the deformable nonconductive substrate hasan elasticity in the direction of elongation of at least about 0.0008MPa.
 4. An article according to claim 1 wherein the conductivestretchable ink has a conductivity of from about 0.01 μS to about 100MS.
 5. An article according to claim 1 wherein the conductivestretchable ink comprises a fluoroelastomer.
 6. An article according toclaim 5 wherein the fluoroelastomer is (a) a copolymer of vinylidenefluoride and hexafluoropropylene; (b) a terpolymer of vinylidenefluoride, hexafluoropropylene, and tetrafluoroethylene; (c) a copolymerof vinylidene fluoride and (per)fluoromethoxyalkylvinylether (d) aterpolymer of vinylidene fluoride, hexafluoropropylene, andpolyperfluoromethylvinylether; (e) a terpolymer of vinylidene fluoride,tetrafluoroethylene, and a fluorinated vinyl ether; (f) a terpolymer ofvinylidene fluoride, tetrafluoroethylene, and propylene; (g) atetrapolymer of vinylidene fluoride, hexafluoropropylene,tetrafluoroethylene, and polyperfluoromethylvinylether; (h) a terpolymerof tetrafluoroethylene, propylene, and vinylidene fluoride; (i) apentapolymer of tetrafluoroethylene, hexafluoroethylene, vinylidenefluoride, ethylene, and polyperfluoromethylvinylether; or (j) a mixturethereof.
 7. An article according to claim 5 wherein the ink furthercomprises a surfactant.
 8. An article according to claim 1 wherein theconductive stretchable ink comprises a conductive pigment selected fromcarbon black, polypyrrole, polyacetylene, polyaniline, polyphenylenevinylene, polythiophene, polyphenylene sulfide, graphene, silvernanoparticles, copper nanoparticles, or mixtures thereof.
 9. An articleaccording to claim 1 wherein the conductive stretchable ink issubstantially free of silver nanoparticles and copper nanoparticles. 10.An article according to claim 1 wherein the conductive stretchable inkis substantially free of silver nanoparticles.
 11. An article accordingto claim 1 wherein the imagewise pattern comprises: (a) a first set ofat least two non-crossing lines of a conductive stretchable ink on afirst surface of the deformable nonconductive substrate; and (b) asecond set of at least two non-crossing lines of a conductivestretchable ink on a second surface of the deformable nonconductivesubstrate; wherein at least some of the first set of lines on the firstsurface cross at least some of the second set of lines on the secondsurface; and wherein the external circuit connecting the imagewisepattern enables determination of the location of deformation on asurface of the deformable nonconductive substrate.
 12. An articleaccording to claim 11 wherein the conductive stretchable ink comprises afluoroelastomer.
 13. An article according to claim 11 wherein theconductive stretchable ink comprises a conductive pigment selected fromcarbon black, polypyrrole, polyacetylene, polyaniline, polyphenylenevinylene, polythiophene, polyphenylene sulfide, graphene, silvernanoparticles, copper nanoparticles, or mixtures thereof.
 14. An articleaccording to claim 1 wherein the imagewise pattern comprises at leastone line of the conductive stretchable ink on at least one surface ofthe deformable nonconductive substrate, and wherein the external circuitconnecting the imagewise pattern enables determination of the mass of anobject situated on the deformable nonconductive substrate.
 15. Anarticle according to claim 14 wherein the conductive stretchable inkcomprises a fluoroelastomer.
 16. An article according to claim 14wherein the conductive stretchable ink comprises a conductive pigmentselected from carbon black, polypyrrole, polyacetylene, polyaniline,polyphenylene vinylene, polythiophene, polyphenylene sulfide, graphene,silver nanoparticles, copper nanoparticles, or mixtures thereof.
 17. Apatterned article comprising: (1) a deformable nonconductive substratehaving a resistivity of at least about 1.8×10⁵ Ωm and an elasticity inthe direction of elongation of at least about 0.0008 MPa; (2) animagewise pattern thereon of a conductive stretchable ink having aconductivity of from about 0.01 μS to about 100 MS and comprising afluoroelastomer; and (3) an external circuit connecting the imagewisepattern, said external circuit being capable of measuring the electricalresistance across regions of the deformable nonconductive substrate anddetermining the degree of deformation thereof.
 18. A process whichcomprises: (a) applying to a deformable nonconductive substrate in animagewise pattern a conductive stretchable ink; (b) connecting theimagewise pattern with an external circuit; and (c) measuring theelectrical resistance across regions of the deformable nonconductivesubstrate and determining the degree of deformation thereof.
 19. Aprocess according to claim 18 wherein the imagewise pattern comprises:(a) a first set of at least two non-crossing lines of a conductivestretchable ink on a first surface of the deformable nonconductivesubstrate; and (b) a second set of at least two non-crossing lines of aconductive stretchable ink on a second surface of the deformablenonconductive substrate; wherein at least some of the first set of lineson the first surface cross at least some of the second set of lines onthe second surface; and wherein measuring the electrical resistanceacross regions of the deformable nonconductive substrate enablesdetermination of the location of deformation on a surface of thedeformable nonconductive substrate.
 20. A process according to claim 18wherein the imagewise pattern comprises at least one line of theconductive stretchable ink on at least one surface of the deformablenonconductive substrate, and wherein measuring the electrical resistanceacross regions of the deformable nonconductive substrate enablesdetermination of the mass of an object situated on the deformablenonconductive substrate.